This invention relates to the transfer of television pictures onto cine film.
Hitherto the process of transferring television pictures onto cine film has been carried out using a free running cine camera which films from the television screen. Such a process is often preferred to that of recording onto video tape, since cine film is more readily edited and facilitates the projection of larger images as required in lecture threatres and cinemas. However in the filming process a problem arises because the blanking time of the television field scan, which is in the order of 2 milliseconds, is far less than the pull-down time for each cine frame of conventional cine cameras, which is typically in excess of 20 milliseconds. This results in an arbitrary overlapping of the television fields recorded by the camera and is seen as a light or dark horizontal bar which moves up or down the film record depending on the relationship between the camera speed and television field frequency. To overcome this problem on a field scan operating at mains frequency, cine cameras on a mains supply have been modified to operate at 162/3 frames per second, and to film only two field scans out of every three. The period of the omitted scan is used to provide the pull-down time for the cine camera.
The above process is unsuitable for field scans operating at other than mains frequency and also produces a shadowy black bar extending horizontally across each frame of cine film; this occurs because the time at which the camera shutter opens is not coincident with the beginning of a field scan.